In general, most parts of fish heads are disposed of as waste. For example, description will be given on salmon heads, nasal cartilage of a salmon head has been commercialized in the form of so-called “namasu (vinegared or marinated slices of salmon nasal cartilage)”. However, most other parts of the salmon head have been disposed of.
In this connection, fish heads include useful portions such as head cartilage, portions around eyes, brain, pituitary gland (hypophysis) containing growth (somatotropic) hormone and genadotropic hormone, and the like. Techniques to utilize useful substances contained in such useful portions have been being developed.
When such useful portions are collected, for example, pituitaries (hypophyses) rich in growth hormone and genadotropic hormone are collected, there has generally been employed in a laboratory or the like a method which comprises manually cutting a fish head with, for example, a cooking knife, visually locating a pituitary (hypophysis), and collecting the pituitary. Further, there has been tried a method which comprises cutting out a pituitary-containing portion with a cylindrical cutting blade in the direction from a dorsal portion of a fish head to a lower jaw of the fish head, and manually extracting the pituitary from the cut out portion. Moreover, there has been employed, but rarely, a method which comprises removing branchiae from a fish head to expose a mouth and throat of a fish head, and then manually cutting out a pituitary-containing portion with a cylindrical cutting blade in the direction opposite to the above-described direction, i.e., the direction from the exposed throat of the fish head to a dorsal portion of the fish head.
Furthermore, there has heretofore been known a technique to automatically take out useful portions from fish heads although this is not such a technique to collect pituitaries as described above. As the technique to automatically take out useful portions from fish heads, for example, a technique disclosed in Patent Document 1 has been known.
This is a technique to take out nasal cartilage from fish heads which comprises cooking or steaming fish heads to soften the fish heads, placing the fish heads in a rotating mesh drum, rotating the rotating drum to apply impactive force to the fish heads and to thereby expel the residual matter other than the nasal cartilage through the mesh, and taking out the nasal cartilage from the rotating drum. The nasal cartilage is utilized as a starting material for extraction of chondroitin sulfate, and the residual matter is used as a feed or the like.
Further, as a technique to automatically take out useful portions from fish heads, for example, a technique disclosed in Patent Document 2 has also been known.
This is a technique to collect orbital fat (corps adiposum orbitae) from fish heads W, as shown in FIG. 16, in which a conveyer 100 for transferring the fish heads W with their mouths oriented toward the transfer direction is provided, and holders 101 for holding the fish heads W are disposed on the conveyer 100, and a pipe-like extracting blade 102, which has such an inner diameter that blade covers orbits (eye sockets) and which has its tip edged, is placed on one side of the fish heads W held by the holders 101, and the extracting blade 102 is thrust through a fish head W which is transferred to collect eyes together with the surrounding thereof from the fish head W.    Patent Document 1: Japanese Unexamined Patent Publication    Patent Document 2: Japanese Unexamined Patent Publication No. Hei 6 (1994)-153774